Green Hydrogen: Perspectives and Challenges in Using the Natural Gas Network in Ceará/Brazil

Climate change, mainly caused by the use of non-renewable fuels, has raised global concerns and led to the search for less polluting energy sources, making hydrogen a promising energy alternative with the potential to contribute to changes in the energy mix of various countries through the use of technologies that enable its production and use with low or zero carbon emissions. In this context, Brazil has aroused great interest from other countries in exploring its renewable resources for the production of hydrogen (green hydrogen). In this sense, the use of natural gas pipelines and the use of hydrogen in mixtures with natural gas have become the subject of studies due to their economically viable alternative for the immediate use of this energy vector. However, there are still technical and regulatory challenges regarding the integration of hydrogen into the existing natural gas pipeline network. In this context, the present study aims to address the effects of hydrogen interaction with the structure of natural gas pipeline steel and the regulatory barriers to the use of this network for the transportation of green hydrogen, particularly in the state of Ceará/Brazil. After extensive analysis of literature and regulatory documents, it was concluded that: 1) Ceará/Brazil has strong potential to meet the demand for green hydrogen through the use of solar and wind energy sources;2) there is feasibility for the adaptation or conversion of natural gas infrastructure for the transportation of green hydrogen;3) discussions regarding the regulatory competence of green hydrogen transportation and distribution through the natural gas network in Brazil are still incipient;4) the current regulation of the natural gas industry can serve as a subsidy for the regulation of green hydrogen and natural gas transportation.

Feasibility Analysis of Typical Cryogenic Processes for Hydrogen-Mixed Natural Gas Separation

Hydrogen energy is a crucial carrier for the growth of the energy system and its low-carbon transformation.Using natural gas as a carrier of hydrogen transport and the natural gas pipeline network for transportation is a significant step toward realizing large-scale and long-distance hydrogen transport.Hydrogen-mixed natural gas is mainly separated into hydrogen and natural gas by physical methods at present.High purity of hydrogen recovery,but the recovery rate is low.At the same time,compared with natural gas,liquefied natural gas is more economical and flexible.This study analyzes three typical cryogenic separation processes.The results show that the hydrogen separation efficiency and specific energy consumption increase and the liquefaction rate and energy consumption decrease as the hydrogen ratio increases.The energy consumption and specific energy consumption of C3-MRC are lower than the MRC and the cascade liquefaction processes.Besides,as the pressure increases in the C3-MRC liquefaction process,the liquefaction and hydrogen separation efficiency increase and subsequently drop.Different hydrogen content has the highest hydrogen separation efficiency and liquefaction efficiency under different feed gas pressure conditions.The total exergy losses of the C3-MRC are the least in different hydrogen fractions,which are 37.59%and 21.77%less in the 25%hydrogen fraction,and 37.89%and 21.37%less in the 30%hydrogen fraction.Moreover,the exergy efficiency of C3-MRC are 87.68%and 88.06%when the hydrogen fraction are 25%and 30%,higher than the other two processes,which implies that in 25%and 30%fractions,making it more suitable for separate the hydrogen by the cryogenic separation.

Water Role and Its Influence on Hydrogen Isotopic Composition of Natural Gas during Gas Generation

In order to discuss the role and influence of water during the generation of natural gas,the participation mechanism of water during the evolution of organic matter and its influences were summarized.In addition,we carried out an anhydrous cracking experiment of oil extracted from the Feixianguan Formation source rock in a closed system,which led to the establishment of the kinetic models for describing carbon and hydrogen isotopic fractionation during gas generation from organic matter.The models were calibrated and then applied to the northeastern Sichuan Basin.By combining a series of gas generation experiments from octadecane pyrolysis without water or with distilled water in varying mass proportions,several results were proved:(1) the hydrogen isotopic composition of natural gas becomes lighter with the participation of formation water;(2) we can quantitatively study the hydrogen isotopic fractionation with the kinetic model for describing carbon isotopic fractionation; (3) more abundant and reliable geological information can be obtained through the combined application of carbon and hydrogen isotopic indices.

CO_2 selective hydrogenation to synthetic natural gas(SNG) over four nano-sized Ni/ZrO_2 samples:ZrO_2 crystalline phase & treatment impact

Two type zirconia (monoclinic and tetragonal phase ZrO2) carriers were synthesized via hydrothermal route, and nano-sized zirconia supported nickel catalysts were prepared by incipient impregnation then followed thermal treatment at 300 °C to 500 °C, for the CO2selective hydrogenation to synthetic natural gas (SNG). The catalysts were characterized by XRD, CO2-TPD-MS, XPS, TPSR (CH4, CO2) techniques. For comparison, the catalyst NZ-W-400 (monoclinic) synthesized in water solvent exhibited a better catalytic activity than the catalyst NZ-M-400 (tetragonal) prepared in methanol solvent. The catalyst NZ-W-400 displayed more H2absorbed sites, more basic sites and a lower temperature of initial CO2activation. Then, the thermal treatment of monoclinic ZrO2supported nickel precursor was manufactured at three temperature of 350, 400, 500 °C. The TPSR experiments displayed that there were the lower temperature for CO2activation and initial conversion (185 °C) as well as the lower peak temperature of CH4generation (318 °C), for the catalyst calcined at 500 °C. This sample contained the more basic sites and the higher catalytic activity, evidenced byCO2-TPD-MS and performance measurement. As for the NZ-W-350 sample, which exhibited the less basic sites and the lower catalytic activity, its initial temperature for CO2activation and conversion was higher (214 °C) as well as the higher peak temperature of CH4formation (382 °C). © 2016 Science Press

Natural gas and biofuel as feedstock for hydrogen productionon Ni catalysts

In this article, the aptitude of natural gas as feedstock in steam reforming process for hydrogen production is compared with that of different liquid fuels （pure compounds and commercial fuels）, with the aim to investigate the potentialities of biofuels to overcome the CO2 emission problems deriving from fossil fuel processing. The performances of a nickel based catalyst （commercially used in steam reforming of natural gas） were evaluated in terms of feed conversion and yield to the different products as function of temperature, space velocity and water/fuel ratio. Furthermore, a preliminary evaluation of catalyst durability was effected by monitoring yield to H2 versus time on stream and measuring coke formation at the end of experimental tests. High yields to hydrogen were obtained with all fuels investigated, whereas the deactivation phenomena, which are correlated to carbon deposition on the catalyst, were observed with all tested fuels, except for methane and biofuel.

Origins of High H_2S-bearing Natural Gas in China

Natural gas containing hydrogen sulphide （H2S） has been found in several petroliferous basins in China, such as the Sichuan Basin, Bohai Bay Basin, Ordos Basin, Tarim Basin, etc. Natural gas with higher HES contents （HES 〉5 % mol.） is mostly distributed in both the gas reservoirs of Dukouhe, Luojiazhai, Puguang and Tieshanpo, which belong to the Triassic Feixianguan Formation in the northeastern Sichuan Basin and those of the Kongdian-Shahejie formations in the northeastern Jinxian Sag of the Jizhong Depression, Bohai Bay Basin. In the Sichuan Basin, the HES contents of natural gas average over 9% and some can be 17 %, while those of the Bohai Bay Basin range from 40 % to 92 %, being then one of the gas reservoirs with the highest H2S contents in the world. Based on detailed observation and sample analysis results of a total 5000 m of core from over 70 wells in the above-mentioned two basins, especially sulfur isotopic analysis of gypsum, brimstone, pyrite and natural gas, also with integrated study of the geochemical characteristics of hydrocarbons, it is thought that the natural gas with high HES contents resulted from thermochemical sulfate reduction （TSR） reactions. Among them, the natural gas in the Feixianguan Formation resulted from TSR reactions participated by hydrocarbon gas, while that in the Zhaolanzhuang of the Jinxian Sag being the product of TSR participated by crude oil. During the consumption process of hydrocarbons due to TSR, the heavy hydrocarbons were apt to react with sulfate, which accordingly resulted in the dry coefficient of natural gas increasing and the carbon isotopes becoming heavier.

Hydrate capture CO_2 from shifted synthesis gas, flue gas and sour natural gas or biogas

CO2 capture by hydrate formation is a novel gas separation technology, by which CO2 is selectively engaged in the cages of hydrate and is separated with other gases, based on the differences of phase equilibrium for CO2 and other gases. However. rigorous temperature and pressure, high energy cost and industrialized hydration separator dragged the development of the hydrate based CO2 capture. In this paper, the key problems in CO2 capture from the different sources such as shifted synthesis gas, flue gas and sour natural gas or biogas were analyzed. For shifted synthesis gas and flue gas, its high energy consumption is the barrier, and for the sour natural gas or biogas （CO2/CH4 system）, the bottleneck is how to enhance the selectivity of CO2 hydration. For these gases, scale-up is the main difficulty. Also, this paper explored the possibility of separating different gases by selective hydrate formation and reviewed the progress of CO2 separation from shifted synthesis gas, flue gas and sour natural gas or biogas.

Exergy Analysis and Retrofitting of Natural Gas-based Acetylene Process

This article presents an acetylene production process by partial oxidation/combustion of natural gas. The thermodynamic performance and exergy analysis in the process are investigated using the flow-sheeting program Aspen Plus. The results indicate that the most important destruction of exergy is found to occur in the reactor and water quenching scrubber, amounting to 8.23% and 10.39%, respectively, of the entire system. Based on the results of thermodynamic and exergy analysis, the acetylene reactor has been retrofitted. The improvement ratios of molar 02 to CH4 and molar CO to CN4 are 0.65 and 0.20, respectively. An improvement of the acetylene production system is proposed. Adopting the improvement operation conditions and using oil to realize the reaction heat recovery, the feedstock of natural gas is reduced by 9.88% and the exergy loss in the retrofitting process is decreased by 19.71% compared to the original process.

Effect of combining the metals of group VI supported on H-ZSM-5 zeolite as catalysts for non-oxidative conversion of natural gas to petrochemicals

The most prestigious catalyst applied in natural gas （methane） non-oxidative conversion to petrochemicals is 6%Mo/H-ZSM-5. Chromium, molybdenum and tungsten are the group VI metals. Hence, in this work, 6%Mo/H-ZSM-5 was correlated with 3%Cr＋3%Mo/H-ZSM-5 and 3%W＋3%Mo/H-ZSM-5 as catalysts to examine their promoting or inhibiting effects on the various reactions taking place during methane conversion. The catalytic activities of these catalysts were tested in a continuous flow fixed bed reactor at 700℃ and a GHSV of 1500 ml·g^-1·h^-1 Characterization of the catalysts using XRD, TGA and TPD were investigated. XRD and NH3-TPD showed greater interaction between the W-phase and the Bronsted acid sites in the channels of the zeolite than between Cr-phase and the acid sites in the zeolite.

Genetic type and source of natural gas in the southern margin of Junggar Basin, NW China

Natural gas has been discovered in many anticlines in the southern margin of the Junggar Basin. However, the geochemical characteristics of natural gas in different anticlines haven’t been compared systematically, particularly, the type and source of natural gas discovered recently in Well Gaotan-1 at the Gaoquan anticline remain unclear. The gas composition characteristics and carbon and hydrogen isotope compositions in different anticlines were compared and sorted systematically to identify genetic types and source of the natural gas. The results show that most of the gas samples are wet gas, and a few are dry gas;the gas samples from the western and middle parts have relatively heavier carbon isotope composition and lighter hydrogen isotope composition, while the gas samples from the eastern part of southern basin have lighter carbon and hydrogen isotope compositions. The natural gas in the southern margin is thermogenic gas generated by freshwater-brackish water sedimentary organic matter, which can be divided into three types, coal-derived gas, mixed gas and oil-associated gas, in which coal-derived gas and mixed gas take dominance. The Jurassic coal measures is the main natural gas source rock in the southern margin, and the Permian lacustrine and the Upper Triassic lacustrine-limnetic facies source rocks are also important natural gas source rocks. The natural gas in the western part of the southern margin is derived from the Jurassic coal measures and the Permian lacustrine source rock, while the natural gas in the middle part of the southern margin is mainly derived from the Jurassic coal measures, partly from the Permian and/or the Upper Triassic source rocks, and the natural gas in the eastern part of the southern margin is originated from the Permian lacustrine source rock. The natural gas in the Qingshuihe oil and gas reservoir of Well Gaotan-1 is a mixture of coal-derived gas and oil-associated gas, of which the Jurassic and Permian source rocks contribute about half each.

Auctions to reveal consumers’willingness to pay for low-carbon hydrogen projects:combining lessons from renewables and natural-gas industries

Low-carbon hydrogen is expected to play a key role in realizing net-zero and sustainable development plans.Nonetheless,there is a gap between the cost of producing low-carbon hydrogen and its potential users’willingness to pay for such hydrogen.To implement support for the development of the industry,we propose using low-carbon hydrogen long-term agreements allocated through auction mechanisms.The objectives are 2-fold:(i)matching supply and demand volumes considering the time horizon and geographical delivery point specification and(ii)allocating the subsidy.This perspective article innovates by proposing a reference price indexed to liquid to natural-gas prices,which is the main product that low-carbon hydrogen aims to substitute.The premium and the production cost are defined through a double-sided auction.This aims to minimize the public policy funds required to incentivize the low-carbon hydrogen market while facilitating long-term agreements and mitigating price risks that may hinder investment.

Underground coal gasification and its strategic significance to the development of natural gas industry in China

Based on the present situation and trend of underground coal gasification in China and overseas, this article puts forward the basic concept, mechanism and mode of underground coal gasification, and presents the challenges, development potential and development path now faced. In China, underground coal gasification which is in accord with the clean utilization of coal can produce "artificial gas", which provides a new strategic approach to supply methane and hydrogen with Chinese characteristics before new energy sources offer large-scale supply. Coal measure strata in oil-bearing basins are developed in China, with 3.77 trillion tons coal reserves for the buried depth of 1000-3 000 m. It is initially expected that the amount of natural gas resources from underground coal gasification to be 272-332 trillion cubic meters, which are about triple the sum of conventional natural gas, or equivalent to the total unconventional natural gas resources. According to the differences of coal reaction mechanism and product composition of underground coal gasification, the underground coal gasification can be divided into three development modes, hydrogen-rich in shallow, methane-rich in medium and deep,supercritical hydrogen-rich in deep. Beyond the scope of underground mining of coal enterprises, petroleum and petrochemical enterprises can take their own integration advantages of technologies, pipeline, market and so on, to develop underground coal gasification business based on their different needs and technical maturity, to effectively exploit a large amount of coal resources cleanly and to alleviate the tight supply of natural gas. It can also be combined with using the produced hydrogen in nearby area and the CO_2 flooding and storage in adjacent oil areas to create a demonstration zone for net zero emissions of petroleum and petrochemical recycling economy. It is significant for reserving resources and technologies for the coming "hydrogen economy" era, and opening up a new path for China's "clean, low carbon, safe and efficient" modern energy system construction.

Feasibility analysis of using biomass gas or hydrogenin the tobacco curing system

To address the energy shortage and meet the requirements of environmental protection policies,the feasibility of premixed fuel 1(natural gas(NG),syngas,and hydrogen)and premixed fuel 2(NG and hydrogen)in the tobacco curing system was studied.First,according to the law of conservation of energy and mass,a tobacco leaf curing system model was established.Then,the interchangeability index of the premixed fuels was analyzed,and their volume ratios were obtained.Finally,a numerical simulation analysis of the premixed fuel combustion was conducted based on the indicators of emission,temperature,and economy.On this basis,the comprehensive performance indexes of the system composed of different premixed fuels were evaluated.The results obtained indicate that with the increase in the hydrogen volume ratio in premixed fuel 1,NO_(X) emissions will gradually increase.Moreover,with the increase in the hydrogen volume ratio in premixed fuel 2,CO emissions will gradually decrease.Because premixed fuel 2 contains more hydrogen than premixed fuel 1,CO emissions are reduced by 9.39%and 16.72%as compared with the NG system when the volume ratio of NG to hydrogen is 95∶5 and 90∶10,but the NO emissions of the latter are beyond the acceptable range.Finally,the overall performance is good when the volume ratio of NG to hydrogen is 95∶5,and the volume ratio of NG to syngas to hydrogen is 90∶5∶5.

大口径长输天然气管道掺氢混气特性研究

长输天然气管道具有管径大、流速快的特点,掺氢混气的不均匀度会增加管道输送系统金属氢脆、密封渗漏、设备运行不稳定等风险。针对我国某长输天然气管道的运行工况,采用数值模拟的方法研究了4种静态混合器(SK型、SX型、SL型、HEV型)进行掺氢输送(掺氢比为3%)时的流场特性以及混合效果。结果表明,4种静态混合器对天然气掺氢混气均具有扰动混合作用,混合不均匀度随输量的增大而减小,压力损失随输量的增大而增大;在掺氢比为3%、掺氢压力为4.22 MPa、输量为13×10^(8)~36×10^(8)Nm^(3)/a的工况下,SK型、SX型、SL型和HEV型静态混合器的混合特性和效果差异较大,应在不同的混合距离处,将混合不均匀度下降至5%以下。综合考虑,可优选或创新设计结构相对简单、混合距离短、混合不均匀度较低、湍流特性优异、剪切特性良好并且压降适中的静态混合器,作为大口径长输天然气主管路掺氢混合器。

隧道内埋地掺氢天然气管道泄漏扩散研究

氢能作为一种理想的清洁能源备受青睐,将氢气掺入到天然气管道中是实现氢能大规模输送的有效途径。在输送过程中,管道一旦发生泄漏便会严重影响管道的安全运行,目前隧道内埋地掺氢天然气管道的泄漏扩散规律尚不明确。建立了隧道内埋地掺氢天然气管道泄漏扩散数值模型,探究了掺氢比(体积分数)、泄漏孔径和来流风速对混合气体泄漏扩散特性的影响。结果表明,掺氢天然气泄漏后在隧道顶部大量积聚,呈现出中心区域浓度高、边缘区域浓度低的现象。随着掺氢比增大,混合气体爆炸下限降低,相同时间内的泄漏量增多。因隧道空间密闭,混合气体在短时间内不能充分扩散,因此掺氢比越大,爆炸危险区域越大,达到爆炸极限的时间越短。当掺氢比由5%增加到20%时,爆炸危险区域增加了3.18%,混合气体达到爆炸极限的时间缩短了3.7%。泄漏孔径越大,混合气体泄漏量越大,爆炸危险区域越大,混合气体达到爆炸极限的时间越短。当泄漏孔径由20 mm增大至100 mm时,沿隧道径向的爆炸危险区域由距地面1.49 m减小至0.30 m,轴向爆炸危险区域由13.4 m增大至91.9 m,达到爆炸极限的时间由95.2 s缩短至11.3 s。来流风速的平流输送作用促进了混合气体沿隧道轴向的扩散,缩小了隧道顶部的高浓度区域,爆炸危险区域显著缩小。当来流风速由0.5 m/s增大至2.0 m/s时,爆炸危险区域缩小了81.7%。因此,隧道内气体发生泄漏时应及时通风,避免燃烧爆炸等事故的发生。该研究结果可为隧道内埋地掺氢天然气管道的安全运行提供理论依据。

掺氢天然气喷射火燃烧特性数值模拟研究

为探究掺氢天然气的燃烧特性,基于OpenFOAM开源平台建立掺氢天然气数值模拟方法,采用大涡模拟(LES)模型、有限速率燃烧模型(Pasr)模型和单步反应模型对掺氢天然气喷射火的燃烧过程进行数值模拟。研究结果表明:喷射火的火焰最高温度与掺氢比之间表现为正相关关系,火焰长度与掺氢比之间表现为负相关关系;此外,研究发现随着射流速度增加,轴线上火焰温度高温区域逐渐变远,在同等掺氢比条件下,当射流速度由30 m/s增加至60 m/s时,火焰长度变化区间由1.0~1.2512 m增加至1.2502~1.5612 m,火焰长度与射流速度间表现出正相关关系。研究结果可为实际应用中的燃烧器设计和掺氢天然气泄漏与爆燃事故风险防控提供重要的理论指导。

基于回归模型的掺氢天然气压缩因子计算方法

压缩因子回归模型结构简单、计算快捷,在常规天然气压缩因子计算中更易程序化。文中研究掺氢天然气的应用并与其他模型对比。回归模型包括三次方、幂指数等多种形式,如HY(Hall-Yarborough)、RK(Redlich-Kwong)模型等,各模型适用的压力和温度范围各不相同。采用文献391组掺氢天然气压缩因子实验数据,对比分析7种回归模型在不同掺氢比例、压力和温度范围下的计算精度,并与GERG-2008状态方程进行对比。其中压力范围为0.1—10 MPa、温度为210—350 K、掺氢摩尔分数0—100%。结果表明:RK的平均相对误差为1.36%、HY为1.46%,均小于GERG-2008(1.47%);在T>298.15 K时,HY模型的误差最小;在T<298.15 K时,RK模型的计算误差最小;在不同掺氢比例下,HY和RK的最大平均相对误差分别为2.73%和1.58%,小于GERG-2008(3.54%)。相较于其他回归模型,建立的HY-RK组合回归模型更适用于掺氢天然气的压缩因子计算。

Structure and Vibrational Spectroscopy of 2-Methylallyl Alcohol

The intramolecular O−H…πhydrogen bond has garnered significant research interest in recent decades.In this work,we utilized the infrared(IR)-vacuum-ultraviolet(VUV)nonresonant ionization detected IR spectroscopy(NRID-IR)method to study the molecular structure of neutral and cationic 2-methylallyl alcohol(MAA,CH_(2)=C(CH_(3))−CH_(2)−OH).Density functional theory calculations revealed five stable neutral and three stable cationic MAA conformers,respectively.Two neutral MAA conformers are expected to have an O−H…πintramolecular hydrogen bond interaction,based on the structural characterization that the OH group is directed toward the C=C double bond.The IR spectra of both neutral(2700−3700 cm^(−1))and cationic MAA(2500−7200 cm^(−1))were measured,and the anharmonic IR spectra were calculated at the B3LYP-D3(BJ)/def2-TZVPP level.The OH stretching vibration frequency of neutral MAA was observed at 3656 cm−1,slightly lower than those of methanol and ethanol.In contrast,the OH stretching vibration of cationic MAA was red-shifted by about 140 cm^(−1)compared to neutral MAA.The interaction region indicator and natural bond orbital analysis suggest that the O−H…πinteraction in neutral MAA is weak,and may not play a major role in stabilizing the neutral MAA.

掺氢天然气输送管线钢氢脆行为的研究进展

近年来,利用现有的天然气管网输送氢气以其经济性和高效性受到国内外研究学者的广泛关注。但是,氢气导致管线钢的氢脆问题给管道的长期安全运行带来极大的挑战,掺氢天然气输送管线钢的氢脆行为研究迫在眉睫。综述了金属氢脆机理的研究进展,对氢气/掺氢天然气环境中管线钢金属力学性能变化等方面的研究现状进行总结。此外,还介绍了抑制管线钢氢脆行为的常用方法,为氢脆问题的有效解决提供参考,从而保障天然气输送管道的安全运行。

掺氢天然气管道本体及焊缝裂纹扩展研究进展

天然气管道掺氢输送是实现大规模输氢的有效方式,然而管道钢本体及焊缝在渗氢后会因氢脆而裂纹扩展加剧。综述了不同氢分压、加载频率、残余应力等条件下,管道本体与焊缝渗氢后的裂纹扩展试验研究进展,总结了渗氢钢材的裂纹扩展机制,分析了钢材裂纹扩展的理论和唯象模型,介绍了分子动力学模拟、有限元方法等数值模拟技术在掺氢钢材裂纹扩展研究领域的应用。对照天然气管道掺氢输送后本体及焊缝的安全性管理需求,分析了试验、理论及数值模拟三方面研究在预测和防止管道裂纹扩展方面存在的不足,阐明了下一步研究的机遇与挑战,提出了试验、理论及模拟三方面的协同研究方法,为维护掺氢天然气管道运行全生命周期的安全提供了借鉴。